A common approach to crop harvesting involves the use of a combine having a header on its forward portion for engaging and removing the crop from a field. The header is maintained a designated height above the soil as determined by the type of crop and various operating conditions. Operating with the header too high will result in failure to harvest all of the crop, while operating too close to the soil increases the possibility of damage to the header by impact with rocks and other obstructions in the soil. With the use of longer headers spanning wider tracts, the possibility of impact of the header with the soil and consequent damage to the header and/or combine has correspondingly increased.
Various types of height sensors are used to maintain the harvesting machine a designated height above the soil for optimum crop recovery. Most current height sensors employ a ground engaging arm suspended from the header and extending rearwardly relative to the direction of travel. A cutter assembly is located in a bottom portion of the header housing forward of the height sensor arm. Thus, the sensor arm provides information regarding vertical separation between the cutter assembly and the soil with respect to soil the cutter assembly has already passed over. The inability to sense and provide information regarding terrain in front of the header limits the accuracy of the height control signals provided by the height sensor. Moreover, as the header gets closer to the ground, current sensor arms engage the ground even further aft of the cutter assembly thus increasing the separation between the position of the cutter assembly and the location of the soil the height of which is actually being detected.
The height sensor typically includes a thin rod extending rearwardly and engaging the soil. These sensor arms are subjected to large forces. For example, a downward force is applied to the sensor arm to ensure that its distal end engages the soil. This downward force is of sufficient magnitude to allow the arm to penetrate plant residue in order to contact the soil. In addition, crop rows are frequently curvilinear to accommodate terrain contour. Harvesting curvilinear crop rows results in the application of large lateral forces on the sensor arm. The capability of combines, which incorporate rear steering, to rapidly turn and change direction increases the likelihood of sensor arm damage caused by the application of large lateral forces. In addition, field terracing wherein upraised strips of soil or elongated shallow depressions, or ditches, in the soil are formed in a spaced manner over a field are increasingly used to reduce erosion. Traversing these upraised strips of soil or spaced depressions also subjects the height sensor arm to large forces while placing greater demands on sensing and reacting to changes in soil elevation to avoid damage to harvesting machinery. Also, in an attempt to maximize crop recovery, harvesting headers are increasingly being employed at lower heights above the soil with increased force being applied to the height sensor arm. All of these factors tend to increase the likelihood of damage to the height control sensor resulting in harvester down time and production losses.
Finally, header height control sensors are generally not designed with the configuration of existing headers as a primary consideration. Thus, the typical header height sensor is not adapted for retrofitting on an existing header without header modification. For example, one current soil height sensor employs a pair of pivotally connected curved arms mounted to a lower portion of the header housing. In order to accommodate this multi-section height sensor arm, the lower surface of the header housing is provided with a recessed portion to receive the arm sections for storage and protection of the arms from damage when not in use. Not all harvester heads are provided with these height sensor arm storage recesses, thus, limiting the use of this type of sensor arm to headers having these recesses.
The present invention addresses the aforementioned limitations of the prior art by providing a height sensor arrangement particularly adapted for use in agricultural applications such as on a harvester which provides an increasingly early warning of upraised soil about to be traversed by the harvester as its height above the soil is reduced. This allows for more accurate height positioning of the harvester, thus reducing the possibility of impact with the soil and damage to the harvester. The height control sensor arrangement is particularly adapted for positioning in a forward, lower portion of the harvester to provide an even earlier warning of upraised soil to allow for harvester height adjustment.